A magnetic memory device is a semiconductor device that may perform write and read operations at relatively high speeds and that may provide relatively high integration. In addition, a magnetic memory device may efficiently perform re-write operations and may provide nonvolatile memory storage. Usage of magnetic memory devices is thus increasing.
In general, a magnetic memory device uses a magnetic tunnel junction (MTJ) memory cell as a data storing element. An MTJ memory cell may include two ferromagnetic materials and an insulator positioned between the two ferromagnetic materials. A resistance of an MTJ memory cell may be changed according to magnetization directions of the two ferromagnetic materials. That is, the resistance of the MTJ memory cell may be smaller when the magnetization directions of the two ferromagnetic materials are the same than when the magnetization directions thereof are different. Whether information stored in a memory cell of a magnetic memory device is logic ‘1’ or logic ‘0’ may be determined by sensing a magnitude of current flowing through the MTJ memory cell resulting from variations of the resistance.
A conventional magnetic memory device including a MJT memory cell is schematically shown in FIG. 1. Referring to FIG. 1, the magnetic memory device includes an MTJ memory cell 11, a digit line 1, and a bit line 13. The digit line 1 is disposed below the MTJ memory cell 11 with a predetermined gap therebetween. The bit line 13 contacts the top surface of the MTJ memory cell 11 and crosses an upper portion of the digit line 1. The MTJ memory cell 11 is disposed at the intersection of the digit line 1 and the bit line 13. The bottom surface of the MTJ memory cell 11 is electrically connected to a switching element (not shown) such as a MOS transistor via an electrode 3.
The MTJ memory cell 11 includes a lower magnetic pattern 5, an insulation pattern 7, and an upper magnetic pattern 9 that are sequentially stacked. A magnetization direction of the lower magnetic pattern 5 is fixed, but a magnetization direction of the upper magnetic pattern 9 is changeable according to an applied magnetic field.
Operations of writing data on the magnetic memory device will now be briefly discussed. A predetermined current is applied to the digit line 1 and the bit line 13, respectively, to form magnetic fields around the digit line 1 and the bit line 13. The vector sum of the magnetic field formed around the digit line 1 and the magnetic field formed around the bit line 13 is applied to the MTJ memory cell 11, thereby changing the magnetization direction of the upper magnetic pattern 9.
With increasing integration densities of semiconductor devices, sizes of MTJ memory cells 11 may be gradually reduced. As the size of an MTJ memory cell 11 decreases, a strength of the magnetic field used to change magnetization directions of the MTJ memory cell 11 increases, thereby increasing an amount of current applied to the digit line 1 and the bit line 13 for the write operation of the magnetic memory device. As a result, power consumption of the magnetic memory device may increase.